Process of manufacturing tungsten carbide



Nov. 15, 1932. o. F. MARVIN 1,887,729

.nocassl or muumc'runme Tunesm; 01mm; Filed Feb. 3, Iss6 ATTORNEY INVENTOR" Patented Nov. 15, 1932 UNITED STATES PATENT OFFICE Om 1'. mm, L08 AHGELES, ASSIGNOB 1'0 KILLS ALLOYS, INC 01' LOB ANGELES, CALIFORNIA, A CORPORATION 01' DELAWARE PROCESS 0] MANUFACTURING TUNGSTEN CARBIDE Application fled February a, mo. Serial no. 425,531.

This invention relates to the manufacture of tungsten carbide.

Tungsten carbide is now well-known. It is a chemical composition of great hardness and having a ve high meltin point. For

these reasons it is avored as an a rasive, since if properly made, it is almost. as hard as a diamond, yet it is considerably less expensive. To obtain a high grade product, it isnow known that a tungsten mixture can be melted under the action of a-carbon electric arc, and when the chemicalreaction is-complete, the molten alloy is rapidly chilled b casting it into cool molds. This has been ound essential, because of the peculiar characteristicsof tungsten and its carbides. If the cooling is germitted to take place slowly, there is a tenency for the chemical reaction to reverse, and even if this does not occur, the fineness of the ain structure is materially reduced.

Ti e electric furnace that can produce the molten tungsten carbide must also be such as will produce quick,.uniform heating, as

the temperatures re uired are from 5000 to. kn

2Q 6000 degrees Fahren eit. One such furnace is described in the Mills Patent No.,1,719,558, issued July 2, 1929. In that atent, the necessity of using a cool mold'is isclosed.

:Due to the extreme tem eratures enoounof gas may result in numerous pores and blow:

holes, which are of course detrimental. Furthermore, there is a tendency for the tungsten carbide to react chemically with the carquent reduction in quality.

It is one of the objects of my invention to overcome these disadvantages of the graphite molds, and especially by the use of a mold made from a material that is chemically in- "any appreciable pores or blow holes.

bon, causing overcarburization and conseert even at the high temperatures reached during the process of casting.

I find that the metal copper fulfills the requirements quite well. Although it is by no means so hard to melt, yet its thermal conductivity is so high that tungsten carbide can be safely cast in it without any destruction of the molds. This result of course was hardly to be expected; but experience shows that if the molds are made sufliciently massive, the heat dissipation through the copper occurs so flapidly that the copper withstands the high eat.

. Copper, if moderately pure, will not combine with tungsten carbide either mechanical- 1y or chemically; and consequently it will.not form a gas when acting as a chill for tungsten carbide. Therefore, the finished material I has a remarkable density, and is free from Of course, otherlmaterials having physical and chemical properties similar to'copper can be used in place of it; but since so far as I ow, copper has the highest thermal conductivity of any materials, it is to my mind probably the only suitable material for the above inentioned purposes, knownat the present ime. I

In the accompanying drawing I show a. few forms of molds that can be used in practicing my invention. These forms are merely illustrative, and it is obvious that other forms could be used.- The scope of the inventionitself can be best ascertained from the appendedclaims.

Referring to the drawing:

. Figure 1 is a plan view of a split multiple mold, for casting solid bars of tungsten car- 2 shown in place.

In Figs. 1 and 2, I show the mold halves 1 1, 12, in which round bars can be cast. It is seen that a common mold is used for a plurality of the bars, which of course fill the mold spaces 13. The mold is made in two parts merely for convenience in removing the cast bars. It can be clamped together during molding, and can rest of course, on a block 14 of copper. The mold is massive, in comparison with the mold spaces 13, which are usually of the order of an inch or less in diameter. The bars thus cast are used in any desired way; for example, as an abrasive, embedded at the cutting edge of drilling or reaming tools, or the like. The copper used in making the mold should be substantially pure.

In Figs. 3 and 4, the copper mold is shown as comprising a pair of semicircular halves 15, 16. In this case, the mold has a circular hole 17 at the center, which does not extend entirely through the mold parts 15, 16. In

thepresent instance this aperture is shown as tapered, to cast a tapered rod. In order to cast a tubular rod, a central core 18 can be supported inside the aperture 17 and as by being set in a socket at the bottom 19 of the aperture 17. Thus a mold space is formed between aperture 17 and this core, which may be poured with tungsten carbide as indicated by the section lined space 20 in Fig.4.

In this instance also, the mold is split to facilitate removal of the casting. The two halves 15, 16 can be clamped during the process of casting.

my hand. a

ORRIN F. MARVIN.

Since there, is little opportunity for conducting heat away from core 18, it is prefer able to make this part out of graphite. However, the massive copper parts 15, 16 conduct the heat so rapidly that no opportunity exists for any deleterious reactions during the short period of cooling, between the tungsten caride and the graphite core 18.

The tubular rod cast in such a mold may be of any desired size. I have cast some successfully in such molds, which rods were about an inch in external diameter I and several inches long.

I find that when such copper molds as I have described are used, the chilling of the molten tungsten carbide is rapid; there are no blow holes or pores, and the grain structure of. the castings is excellent.

I. claim:

1. A copper mold for casting tungsten carbide.

2. A metal mold for casting tungsten car- 'bide, said mold having high heat conductivity and chemically inert as regards tungsten cara bide.

3. A massive copper mold for casting tungsten carbide. 4

4. A massive metal mold for casting tungsten carbide, said mold having high heat conductivity and chemically inert as regards tungsten carbide.

5. The process which compr ses securing a molten mass of tungsten carbide, and casting mu R 

